Removed a redundant test
Removed a redundant test

It had different meaning long ago
(https://github.com/Raku/old-issue-tracker/issues/2711). But since then
only specialized `gist` and `raku` methods are supposed to evade
autothreading over a Junction. Contrary to them, `Str` and alikes must
autothread and result in a new junction with their outcomes as
eigenstates.

Despite of the long-ago decided shift in meaning, the test was passing
by accident simply meaning that all eigenstates of the resulting LHS
junction are `Str`. Since this behavior is covered by other tests, this
line can be safely removed.

perl6/roast